Impregnation of regenerated cellulose fibers



Patented Feb. 11, 1947 IIVIPREGNATION OF REGENERATED CELLULOSE FIBERS George S. Radford, Norwalk, Comp, and Ira S. Hurd, Abington, Pa., assignors, by direct and mesne assignments, to Riihm & Haas Company, Philadelphia, Pa., a corporation of Delaware No Drawing. Application May 19, 1942, Serial No. 443,634

6 Claims. (Cl. 117-445) This invention relates to the production of cardable, resilient, non-embrittled, regenerated cellulose staple fibers and has for one of its objects the provision of novel regenerated cellulose staple fibers which have certain wool-like characteristics, which may be dyed, and which may be carded, spun, woven, and, if desired, napped on textile machinery now in common use. The fibers are characterized by retention within the body thereof of a sub-surface deposit of a material of resinous or resin-like character in the substantial absence of an external layer or coating in or on the exposed surface, the coating being minimized to such an, extent as to avoid occurrence of a non-porous, hard, brittle or glass-like envelope or film upon the fibers. Under these circumstances the fibers in their treated condition maintain a relatively porous structure throughout, so that they are amenable to dyeing and other finishing treatments, as well as unusually resistant to the usual cleaning operations including both laundering and dry cleaning.

Heretofore, efforts have been made to alter the characteristics of fabrics and yarns, as described in U. S. Patents Nos. 1,734,516 and 2,088,227. It has not been recognized heretofore, however, that staple regenerated cellulose fibers can be resin-treated in bulk in the manner and with the results as hereinafter described. Neither of the above patents, nor any other of which we are aware, suggests a sub-surface impregnated rayon staple fiberor any sort of treated rayon fiber capable of withstanding ordinary mechanical working.

Our preferred procedure comprises impregnationof staple regenerated cellulose fibers under pressure with a true solution of resin-forming components, removal of said solution from the surface of the impregnated fibers, drying of the impregnated fibers below the temperature at which resin formation occurs, and heat-conversion of the said components within the individual fibers. In impregnating regenerated cellulose fibers it is necessary that the resin-forming components be of such a nature that they yield true solutions or molecular solutions. Such solutions permit true impregnation of fibers by allowing the resin-forming components to enter into and through the pores of the regenerated cellulose so that upon subsequent heat-treatment the components will be converted to resin within the fibers themselves.

Suitable resin-forming components comprise urea, thiourea, melamine, or other carbamide type of compound, or mixtures thereof, together with formaldehyde in more than an equivalent amount to form a monomethylol derivative, or phenol and 2 formaldehyde likewise in a, more than equivalent amount, or the primary addition, methylol. or condensation products of these materials, all of which give true solutions, as opposed to colloidal solutions or micellar dispersions, which are in-= capable of penetrating the structure of regenerated cellulose fibers. dissolved usually in water together with a small amount of a. latent catalyst-(i. e. a catalyst from which acid is formed either by thermal decomposition or by reaction) for converting the condensates to insoluble resins, such as ammonium chloride, ammonium phosphate, chloramides, or the like. The action of such catalysts may be controlled by the addition of free ammonia, if desired. There may also be added to the impregnating bath small amounts of constituents which serve as lubricants, such as long-chained quaternary ammonium salts or sulfonated tallow or oils.

The amount of resin-forming components used in the impregnating solution may vary from about 5% to about 20%, but preferably from about 8% to about 12%. When these solutions are applied to regenerated cellulose fibers according to the method here described, and the surface of the fibers is substantially freed from the solution, there is formed within the fibers from about 3% to about 15% of a resinous deposit, based upon the weight of the fibers. For optimum results the deposition in the interior of the fibers is from about 6% to about 10%. Any resinous material on the surface is a minimum. The amount of resin formed within the fibers is determined not only by the concentration of the solutions but also by the saturation of the fibers with the impregnating solutions. A pick-up or retention of to of the solution on the weight of the fibers is our usual practice prior to removal of solution from the exterior of the fibers.

As the first step in improving regenerated cellulose fibres, the fibres are impregnated under pressure. For this purpose the ordinary pressure dyeing type textile equipment, such as a Franklin process machine or 'I'hies dyeing machine, may be used. Periods of treatment of the order of 20 to 45 minutes on a Franklin process machine have been found quite satisfactory. In another method of introducing the resin-forming components into the fibres, an autoclave may be used with a more or less extended period of impregnation and direct pressure at 50 to 100.1bs. per square inch.

Pressure is applied for a length of time sufficient I to insure substantial sub-surface penetration. Higher and lower pressures with shorter and longer times, however, have been found suitable under variation of other conditions-of applica- .Such components are tion. But momentary pressures, such as are developed bysqueeze rolls or mangles used in the treatment of fabrics or cloth, do not accomplish the results attained by us in the treatment of fibers as herein disclosed.

The solution of resin-forming components is applied at relatively low temperatures; as from 30 F. tol" F., and preferably notto exceed 50 F. to 60 F., or, in any event, not exceeding any temperature from 60 F. to 100 F. at and by reason of which the solution materially changes in character. It is to be understood, however, that time, temperature, and pressure as employed in our process are variable factors and are governed by the particular fiber being treated, its denier or other physical characteristics, the nature of the resin-forming components being used, and the particular type of equipment employed. Treatment at relatively low temperatures is preferred to insure with a safe margin the maintenance of a true solution during impregnation, to avoid premature curing, and to minimize surface coating eifects.

After thorough impregnation the fibers are treated to remove resin-forming components from the surface of the fibers, as by a brief hydroextraction, vacuum-extraction, or other method. If desired, the fibers may be rinsed with water or a solution of neutral salts, such as a sodium chloride or sulfate brine. The fibers freed from resin-forming components on the surface are then dried at temperatures lower than the curing temperature of the particular resin-forming constituents employed. Yet drying should be performed as rapidly as possible to prevent difiusion or migration of the resin-forming components onto the surface of the. fibers. Drying may be advantageously conducted on any of the raw stock drying machines as commonly employed in the art for treatment of raw fibers.

After the fibers have been dried, they are heated to cure the resin. Curing may be carried out by any one or more of the methods heretofore employed for the curing of resin-forming constituents, such as by passage of the impregnated fibers over a belt upon which are directed infra red lamps, or the steaming of the fibers, or the fOrcihg of a hot air blast through the mass of fibers. Care should be taken to balance such factors as time and temperature so that a proper cure is effected. Temperatures between 200 F. and that temperature at which the treated fibers will scorch may be used. Temperatures within the range of from about 240 F. to about 320 F. are usually found most desirable from a practical standpoint.

The removal of surface material and the drying and curing of the fibers should be carried out within a reasonably short period of time, that is, within about 8 hours after impregnation of the fibers, as it is particularly important that no appreciable quantity ofr'esin-forming components remains on theexterior surfaces of the fiber or be permitted to difiuse there during the process- Though it is found that our process may be applied to previously dyed fibers, the fibers may be dyed during the foregoing procedure by incorporating in the resin-forming materials a dye compatible with the solution of resin-forming components, such as a so-called fast-to-light direct color. Vat dyeing, of course, could not be carried out at thetime of impregnation because of the alkaline nature of the reduced vat color.

In the preferred practice of the invention, how- 4 ever. dyeing is conducted after the curing operation as above described. This, so far as our experience to date has shown, gives superior results. After such dyeing and a subsequent drying of the fibers, they are then in condition for employment in the usual textile processes of mixing or blending for presentation to the card.

The striking feature of the fibers of this invention is found in the .fact that they may be carded as by ordinaiy revolving flat-top cards or roller-top cards without an objectionable amount of fly. This is due primarily to the lack of any substantial surface coating which would embrittle and diminish the springiness imparted to the fibers by the resin contained therein. Further, it is found in practice that fibers thus carded produce a roving which may be readily spun and woven in the usualtextile processes. It is further found that the fibers of this invention may be employed in the manufacture of brushed, napped, and pile fabrics in that they are not objectionably affected by any of the manufacturing steps in connection therewith, or by subsequent use. It is found in practice that fabrics made from the fibers of this inven tion tend to better retain their original manufactured condition, and to far better withstand normal use and cleasing by usual methods.

Example-A batch of lbs. of 3 denier 1 staple regenerated cellulose (viscose) was treated on a Franklin process machine with gallons of a solution containing 15% of dimethylol urea to which had been added of cetyl dimethyl benzyl ammonium chloride and 0.75% of diammonium phosphate. The solution was circulated at a temperature of 55? F. for 40 minutes with a change in direction of flow every 5 minutes. The gauge pressure was 5 lbs. per square inch during flow in one direction and 12 lbs. per square inch during flow in the other. After the 40 minute period, the impregnated stock was removed, briefly hydro-extracted, and dried on a raw stock dryer at F. and then heated for 3 minutes at 315 F., to insolubilise the resin-forming components.

The resiliency of the fibers before and after treatment was evaluated by packing a given weight in a can fitted with a plunger attached to a lever arm having. a weight attached thereto. The recoverability was determined in each case and it was found that the resiliency of the treated fibers was 26% greater than the resiliency of the untreated fibers, thus approachin in resiliency the resiliency of wool of certain grades.

By methods generally similar to those described in the above example there have been applied to viscose staple and to cuprammonium staple, aqueous solutions of the primary condensate obtained from a mixture of equal weights of urea and melamine with formaldehyde and of the watersoluble primary condensate obtained by reacting formaldehyde and phenol in the presence of twotenths mol of sodium hydroxide per mol of phenol to yield a water-soluble methylol derivative. In these treatments there likewise occurred an increase in the resiliency of the fibers of the order of that eifected by the use of dimethylol urea.

We claim:

l. The process of producing cardable, resilient, non-embrittled, staple regenerated cellulose fibers which comprises impregnating at temperatures of 30 F. to 100 F. staple regenerated cellulose fibers in bulk under sustained fluid pressure with a true water solution containing from about 5% to about 20% of aldehyde-condensation resin-forming components and a latentcatalyst for resinifying and hardening said com ponents within said fibers, continuing said impregnating for a period of time suflicient to cause thorough impregnation within the body of the fibers, removing by hydroextracting from the surface of the impregnated fibers substantially all of the said solution occurring thereupon, promptly and rapidly drying the resulting fibers below temperatures at which the resin-forming components will become insolubilized, and heating the dried fibers to effect reaction and insolubilizing of the resin-forming components.

2. The process of producing cardable, resilient, non-embrittled staple regenerated cellulose fibers which comprises impregnating at temperatures between about 30 F. and about 60 F, staple regenerated cellulose fibers in bulk under sustained fiuid pressure with a true water solution containing about 5% to about 20% of aldehyde-condensation resin-forming components and a latent catalyst for resinifying and hardening said components within said fibers, circulating said solution under pressure at said temperature through said fibers 'in bulk for a period of time suificient ing about 6% to 10% of urea-formaldehyde with in the fibers (based on the dry weight thereof), promptly thereafter drying the resulting fibers below temperatures at which insoluble ureaformaldehyde resin forms, and heating the dried, impregnated fibers to effect formation of insoluble urea-formaldehyde resin within the fibers.

' riod of time sufficient to cause thorough impregto cause thorough impregnation of the body of theflbers, removing by hydroextracting and rinsing from the surface of the impregnated fibers substantially all of the said solution occurring thereupon, leaving about 3% to about 15% of resin-forming components within the fibers (on.

the basis of the dry weight thereof), promptly thereafter drying the resulting fibers below temperatures at which the resin-forming components become insolubilized, and heating the dried, impregnated fibers to effect activating of the catalyst and curing of the resin-forming components therein.

3. The process of producing cardable, resilient, non-embrittled staple regenerated cellulose fibers which comprises impregnating at temperatures between about F. and about 60 F. staple regenerated cellulose fibers in bulk under sustained fluid pressure with a true solution in water containing about 8% to about 15% of water-soluble components for forming a urea-formaldehyde resin and a latent catalyst therefor, continuing impregnating for a period of time sufiicient to insure impregnation into the body of the fibers,

removing by hydroextracting from the surface of the impregnated fibers substantially all of the I said solution occurring thereupon, leaving about 6% to 10% of urea-formaldehyde within the fibers (based on the dry weight thereof), promptly and rapidly drying the resulting fibers below temperatures at which the components for forming urea-formaldehyde become insolubilized, and heating the dried fibers to eifect formation of an insoluble urea-formaldehyde condensate therein.

4. The process of producing cardable, resilient, non-embrittled staple regenerated cellulose fibers which comprises impregnating at a temperature between about 30 F. and about 60 F. staple regenerated cellulose fibers in bulk under sustained fiuidpressure with a true solution of about 5% to about 15% of a methylol urea in water, a latent catalyst for forming a urea-formaldehyde resin therefrom, and ammonia, circulating said solution under pressure at said temperature through nation of the body of the fibers, removing by hydroextracting and rinsing from the surface of the impregnated fibers substantially all of said solution occurring thereupon, leaving about 6% to 10% of melamine-formaldehyde within the fibers (based on the weight thereof), promptly thereafter drying rapidly the resulting fibers below temperatures at which insoluble melamineformaldehyde'resin forms, and heating the dried, impregnated fibers to effect formation of insoluble melamine-formaldehyde resin within the fibers.

6. The process of producing cardable, resilient, non embrittled staple regenerated cellulose fibers which comprises impregnating at a temperature between about 30 F. and about 60 F,

of the impregnated fibers substantially all of said solution occurring thereupon, leaving about 6% to 10% of phenol-formaldehyde within the fibers (based on the weight thereof), promptly thereafter drying rapidly the resulting fibers below temperatures at which insoluble phenol-formaldehyde resin forms, and heating the dried, impregnated fibers to effect formation of insoluble phenol-formaldehyde resin within the fibers.

' GEORGE S. RADFORD.

IRA S. HURD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,734,516 Foulds et al Nov. 5, 1929 2,088,227 Battye et al July 27, 1937 2,137,465 Thackston Nov. 22, 1938 2,155,067 Ubbelohde Apr, 18, 1939 2,175,183 Dreyfus et al Oct. 10, 1939 2,208,632 Dreyfus July 23, 1940 2,118,036 Booty May'24, 1938 2,161,805 Dreyfus June 13, 1939 FOREIGN PATENTS Number Country Date 484,691 British Aug. 4, 1936 

